This invention relates generally to a multichannel spark gap system, and more specifically to a system which enhances multichannel spark gaps in which an acoustic standing wave is set up along the electrode which induces a modulation of the gas molecular number density.
Spark gap switches are commonly used in pulse generators to switch the energy in the pulse forming energy store into the load or transmission circuit. In low impedance circuits the switch inductance becomes an important factor in determining the rise time of the pulse. The inductance is determined in the limit by the spacing between the gap electrodes which depends upon the gas density and the operating voltage. Typical values are about 60 nanohenrys per megavolt at 10 amagat of air. This value is for a single spark discharge channel. If the system rise time requirements demand it, one must use multiple switches or spark discharge channels in parallel to lower the inductance. This is commonly done using a rail gap switch, wherein the electrodes are linear rails and the object is to initiate several parallel discharge channels along the length of the rails. This is a statistical process. When the gap is triggered emission sites are initiated on the cathode depending upon the random condition of the fine structure of the cathode surface and the local electric field strength. These sites do not initiate at the same time for these very reasons. When the first site develops into a spark channel and completes the circuit the anode to cathode voltage falls and no further sites can be initiated. Therefore in order to initiate many sites, the rise time of the trigger must be fast in relation to the closure time of the first site. Still the whole process is of a statistical nature and the number and location of the channels established by the trigger pulse is not dependable on a shot to shot basis. Thus, the inductance and rise time will fluctuate accordingly.
Exemplary in the art of spark gap switch technology are the following U.S. Patents, the disclosure of which are incorporated herein by reference:
U.S. Pat. No. 4,267,484 issued to James P. O'Loughlin; PA1 U.S. Pat. No. 4,431,946 issued to James P. O'Loughlin; PA1 U.S. Pat. No. 4,672,259 issued to Riggins et al; PA1 U.S. Pat. No. 4,191,908 issued to Cunningham PA1 U.S. Pat. No. 4,194,138 issued to Johansson et al; PA1 U.S. Pat. No. 3,798,484 issued to Rich; and PA1 U.S. Pat. No. 4,084,208 issued to Bazarian et al.
All of the above-cited references describe developments in spark gap technology. Of particular note are the two James P. O'Loughlin references, which each disclose multi-channel spark gap systems. In all spark gap systems, it is noted that the electrical breakdown criterion of a gas is determined by the ratio of the electric field (E) to the molecular number density (N) to E/N. In conventional gaps the sites where the emission initiates on the cathode, breakdowns are established by the fact that the cathode surface has small irregularities which cause the local field E to be enhanced and thus establishes regions where a higher E/N exists. The gas pressure is static and thus N is the same everywhere. These local E/N enhancements induce the initiations at these sites. Since the discharge erodes the cathode surface, the number and location of these enhanced site areas are random.
In view of the foregoing discussion, it is apparent that there currently exists the need for a system will control the location of the arc channels and thereby distribute the errosion over the entire electrode length. The present invention does this as it introduces a standing wave density distribution within the gas medium of spark gap switches. This results in a controlled distribution of the location of the arc channels, and distributes the erosion over the entire length of the electrodes as discussed below.